Fish have the honour of being the first true vertebrates – our earliest known vertebrate ancestors. Having come from the more advanced examples of the Chordates, these creatures have a long and interesting history on Earth, and are the crucial marine life-forms, that live in vast numbers throughout all of the waters of the planets, in some form or other. The first fossil evidence of Fish, comes from the ancient Palaeozoic Era, of the Cambrian Period – well over 535 million years ago. Firstly, they were small, primitive, jawless and when compared with modern specimens, almost nothing like Fish, as we would recognise them. However, over the millions of years of evolution, and predation of they’re kind by the dominant creatures of the Cambrian, Ordovician and Silurian Periods (the giant ‘creepy-crawlies’) the Fish built on their success in surviving the several minor-to-major scale extinction events around these times, and diversified to dominate the oceans, taking over from the terrifying giant Sea Scorpions and Giant Molluscs (the Orthocones) that had ruled them for the best part of 200 million years. In the Devonian, they had they’re heyday, ‘The Age of Fishes’, and it is speculated that for over 55 million years, from the time of the Devonian to the Carboniferous, and even Early Permian Periods, Fish ruled the waves. Sharks developed, and have been the defining killer-class of this group of animals ever since.